1. Field of the Invention
Cellular growth and differentiation appear to be initiated, promoted, maintained and regulated by a multiplicity of stimulatory, inhibitory and synergistic hormones and factors. The alteration and/or breakdown of the cellular homeostasis mechanism seems to be a basic cause of growth related diseases including neoplasia. There is a considerable interest in the isolation, characterization and mechanism of action of growth modulatory factors (stimulators and inhibitors) because of their potential use in the diagnosis, prognosis and therapy of various diseases, such as cancer, as well as in understanding the basic mechanisms of mitosis, particularly as it may effect cancer.
The detection, isolation and purification of these factors is frequently complicated by the complexity of the mixture, the divergencies of activities of the various components in the mixtures, the sensitivity of components to deactivation by a wide variety of reagents, the potential for having compounds which depend for their activity on the presence of multiple subunits, and the frequent difficulties in providing bioassays for tracking various purification steps. Nevertheless, there have been substantial advances in purification and separation, which advances have aided in the detection and isolation of products of interest.
2. Description of the Prior Art
Beal et al., Cancer Biochem. Biophys. (1979) 3: 93-96 report the presence of peptides in human urine which inhibit growth and DNA synthesis more in transformed cells than in normal cells. Holley et al., Proc. Natl. Acad. Sci. (1980) 77: 5989-5992 describe the purification of epithelial cell growth inhibitors. Letansky, Biosci. Rep. (1982) 2: 39-45 report that peptides purified from bovine placenta inhibit tumor growth and thymidine incorporation in DNA to a greater extent in neoplasms than in normal cells. Chen, Trends Biochem. Sci. (1982) 7: 364-365 reports the isolating of a peptide from ascites fluid with a cancer suppressing property. Redding and Schally, Proc. Natl. Acad. Sci. (1982) 79: 7014-7018 report isolation of purified peptide(s) from porcine hypothalmi which exhibit antimitogenic activity against several normal and tumor cell lines. Most of these factors have not been fully characterized, nor are their primary structures known.